Anchor carrier selection in multi-carrier wireless network

ABSTRACT

Mechanism to receive control signals transmitted from a base station ( 210, 510, 910 ) to the user equipment ( 220, 520, 920 ) in a manner that minimizes power consumption on the user equipment ( 220, 520, 920 ) while still maintaining some acceptable level of performance is described. The user equipment ( 220, 520, 920 ) periodically measures the signal quality of component carriers used by the base station ( 210, 510, 910 ) and requests control signaling (anchor) carrier reselection. Either a single component carrier can be chosen if the single carrier has sufficient quality or multiple component carriers can be selected when the quality of the single quality is low. The anchor carrier reselection may also be triggered to manage the system as a whole. For fast moving user equipments ( 220, 520, 920 ), anchor carrier hopping pattern can be provided to increase robustness and reduce reselection signaling overhead.

This application is the U.S. national phase of International ApplicationNo. PCT/SE2008/050992, filed 3 Sep. 2008, which designated the U.S. andclaims priority to U.S. Application No. 61/039,190, filed 25 Mar. 2008,which are hereby incorporated by reference.

TECHNICAL FIELD

The disclosed technology relates to selecting one or more anchorcarriers for a user equipment in a wireless network.

BACKGROUND

Evolution of cellular systems promise significant data rate increase inthe future, to 1 Gb/s and higher. Higher data rates typically requirelarger system bandwidths. For the IMT (International MobileTelecommunications) advanced (i.e. the fourth generation mobilecommunication) systems, bandwidths up to 100 MHz are being discussed.Unfortunately, the radio spectrum is a limited resource and since manyoperators and systems need to share the same radio resource, finding afree 100 MHz contiguous spectrum is problematic.

One way to address this issue is to aggregate multiple narrow bandwidths(or component carriers) as illustrated in FIG. 1, which can becontiguous or non-contiguous to aggregately achieve the wide bandwidth.In the example of FIG. 1, a 50 MHz bandwidth spectrum is achieved byaggregating individual narrower bandwidth component carriers, which inthis instance are 20 MHz, 20 MHz, and 10 MHz wide carriers. One benefitof such a solution is that it is possible to generate sufficiently largebandwidth for supporting data rates up to and above 1 Gb/s. Furthermore,this solution also makes it possible to adapt the spectrum parts tovarious situations and geographical positions thus making such solutionvery flexible.

A straightforward evolution of current cellular systems, such as LTE(Long Term Evolution), to support contiguous and non-contiguous spectrumis to introduce multi-carriers. That is, for each spectrum “chunk”representing a “legacy LTE” system carrier, a “4G” user equipment can bemade to be capable of receiving multiple number of LTE componentcarriers of different bandwidths transmitted at different carrierfrequencies.

A user equipment needs to listen for layer 1 and 2 (L1, L2) controlsignals to know where (in frequency or subchannels) and/or when (intime) data packets are scheduled to the user equipment. In singlebandwidth systems like the GSM and LTE, the control signals are signaledfrom a serving base station on a single carrier frequency of the servingcell.

The control signaling of the single bandwidth systems can be extended tothe multi-carrier scenario. That is, the user equipment can listen tothe entirety of the aggregated spectrum for the control signals.Although this approach seems to be straightforward, there can be asignificant drawback in terms of the user equipment power consumption.The aggregated spectrum approach, especially the non-contiguous spectrumcase, implies that the radio receiver architecture for the userequipment will become more complicated than for a user equipment that iscapable of only receiving small and contiguous system bandwidths. Thereason is that the front end radio needs to be able to suppress blockingsignal in between the spectrum “chunks”. Different kind of radioarchitecture can be used to handle this problem. However, they typicallyaccompany drawbacks in terms of power consumption compared to standardcontinuous system bandwidth receivers.

SUMMARY

One aspect of the invention is to provide a mechanism so that controlsignals transmitted from the base station are received by the userequipment in a manner that minimizes power consumption on the userequipment while still maintaining some acceptable level of reliabilityand/or performance. To achieve this balance, a minimum amount receivercapacity on the user equipment can be activated that will achieve theacceptable reliability and/or performance.

In the best scenario, a single component carrier will be sufficient forthe user equipment. The user equipment can then use the single componentcarrier as the anchor carrier and put any remaining receiver capacity ina power conservations mode. The anchor carriers carry control signalsfrom the base station to the user equipment.

In less than optimal conditions, the user equipment only turns on asmuch capacity as needed to maintain the acceptable level of performance.For example, if the user equipment includes a plurality of receiverseach adapted to listen on different narrow bandwidth component carriers,multiple receivers may be turned on to listen for control signals onmultiple anchor carriers. As another example, if the user equipmentincludes one or more adaptable bandwidth receivers, the frequency rangeof the receiver or receivers may be adjusted to listen on the multipleanchor carriers.

The user equipment can periodically—rather than continuously—monitor thecarriers from the base station. The periodic monitoring helps to reducepower consumption on the user equipment since the receivers for thosecarriers are not on continuously. When a triggering event occurs, theuser equipment can request a selection (change) of anchor carrier(s) tothe base station.

In an embodiment, the triggering event generally occurs when at leastone of the current non-anchor carriers is better than at least one ofthe current anchor carriers. When the triggering event occurs, a changeoccurs so that the current non-anchor carrier becomes one of the newanchor carriers for the user equipment. If the current non-anchorcarrier is sufficient by itself, then it can be the sole anchor carrier.This allows all other receivers of the user equipment to be put into thepower conservation mode, such as being turned off a majority of time andonly being turned on for periodic monitoring.

Note that minimizing the number of anchor carriers for the userequipment also has the benefit of enhancing system capacity since lessresources (less number of carriers) have to be devoted to the userequipment.

These concepts can be extended to multiple base stations. For example,the user equipment can request switching of anchor carrier(s) not onlyto carriers from a single base station, but also to carrier(s) fromanother base station. That is, soft or softer handover can be requested.

In other aspects, the base station itself can initiate switching ofanchor carriers for load management purposes. Also, carrier hopping canbe implemented, which is a defined sequence of anchor carrier(s) changesover time for a user equipment. The carrier hopping can be especiallyuseful for fast moving user equipments.

Advantages of the embodiments include at least the following. Byintroducing an anchor carrier set selection procedure as described aboveand detailed below, the user equipment—in many cases—can camp on asingle component carrier for decoding the control signaling. This helpsto reduce the current consumption considerably in the radio front end.Also, the user equipment can also select multiple component carriers forcontrol signaling, either from a single cell or multiple cells, if thatis needed for the current radio channel scenario. This provides improvedcontrol signaling robustness. Further, by implementing carrier sethopping, robust control signaling for fast moving user equipments isachieved while reducing signaling overhead. Yet further, by allowinganchor carrier set updates, load on the network can be managedefficiently.

DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments as illustrated in the accompanyingdrawings in which reference characters refer to the same partsthroughout the various views. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating the principles of theinvention.

FIG. 1 illustrates an example aggregation of multiple narrow bandwidthcarriers to an aggregated wide bandwidth carrier;

FIG. 2 illustrates an embodiment of a wireless network in which anchorcarrier(s) for user equipment(s) is(are) selected;

FIG. 3 illustrates an example method to select anchor carrier(s) for auser equipment;

FIG. 4 illustrates an example method to request switching of anchorcarrier(s);

FIG. 5 illustrates another embodiment of a wireless network in whichanchor carrier(s) for user equipment(s) is(are) selected;

FIG. 6 illustrates an example method to select anchor carrier(s) frommultiple base stations for a user equipment;

FIG. 7 illustrates an example method to request switching of anchorcarrier(s) from multiple base stations;

FIG. 8 illustrates an example method facilitate a possible handoff of auser equipment from one base station to another;

FIG. 9 illustrates another embodiment of a wireless network whichfacilitates carrier-hopping;

FIG. 10 illustrates an example method to facilitate carrier-hopping;

FIG. 11 illustrates an example method for load management;

FIG. 12 illustrates an embodiment of a user equipment; and

FIG. 13 illustrates an embodiment of a base station.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particulararchitectures, interfaces, techniques, etc. in order to provide athorough understanding of the present invention. However, it will beapparent to those skilled in the art that the present invention may bepracticed in other embodiments that depart from these specific details.That is, those skilled in the art will be able to devise variousarrangements which, although not explicitly described or shown herein,embody the principles of the invention and are included within itsspirit and scope.

In some instances, detailed descriptions of well-known devices,circuits, and methods are omitted so as not to obscure the descriptionof the present invention with unnecessary detail. All statements hereinreciting principles, aspects, and embodiments of the invention, as wellas specific examples thereof, are intended to encompass both structuraland functional equivalents thereof. Additionally, it is intended thatsuch equivalents include both currently known equivalents as well asequivalents developed in the future, i.e., any elements developed thatperform the same function, regardless of structure.

Thus, for example, it will be appreciated by those skilled in the artthat block diagrams herein can represent conceptual views ofillustrative circuitry embodying the principles of the technology.Similarly, it will be appreciated that any flow charts, state transitiondiagrams, pseudocode, and the like represent various processes which maybe substantially represented in computer readable medium and so executedby a computer or processor, whether or not such computer or processor isexplicitly shown.

The functions of the various elements including functional blockslabeled or described as “processors” or “controllers” may be providedthrough the use of dedicated hardware as well as hardware capable ofexecuting software in association with appropriate software. Whenprovided by a processor, the functions may be provided by a singlededicated processor, by a single shared processor, or by a plurality ofindividual processors, some of which may be shared or distributed.Moreover, explicit use of the term “processor” or “controller” shouldnot be construed to refer exclusively to hardware capable of executingsoftware, and may include, without limitation, digital signal processor(DSP) hardware, read only memory (ROM) for storing software, randomaccess memory (RAM), and non-volatile storage.

In an embodiment, a L1/L2 control signaling component carrier orcarriers reselection procedure is introduced. This can be accomplishedin several ways. In one way, the user equipment can measure, on aregular basis (i.e., periodically), a reliability of a signal onrespective component carriers of the aggregated bandwidth spectrum. Thesignal reliability can be measured in terms of SIR(signal-to-interference ratio), RSRP (reference signal received power),data transmission rate, error rate, repeat request rate, and so on. Ingeneral, any QoS (quality of service) measurement parameters may be usedfor reliability.

Based on the reliability of the component carriers, the user equipmentcan request an anchor carrier reselection to the base station. That is,the user equipment can request a change in the anchor carrier set—whichis a set of carriers that include one or more anchor carriers for theuser equipment. An anchor carrier can be viewed as the carrier thatcarries the control signals, such as the L1/L2 control signals, from thebase station to the user equipment. The control signals inform the userequipment regarding specific downlink and uplink resources (such asidentification of resource blocks of a component carrier) scheduled forthe user equipment, modulation scheme to be used, transmission powerlevel, and so on.

In the anchor carrier reselection, a single component carrier can bechosen or multiple component carriers may be selected to be included inthe anchor carrier set. For example, a single component carrier may havesufficient SIR from the perspective of the user equipment and thus canbe chosen to be the single anchor carrier in the set. If the singlecomponent carrier does not have the sufficient SIR, then multiplecarriers can be selected to be included in the anchor carrier set toachieve the desired SIR.

The anchor carrier selection process may be initiated also for loadmanagement purposes. Typically, a base station is in communication withmultiple user equipments and one component carrier can be used by thebase station to transmit control signals to multiple user equipments.The same component carrier can be used to carry data signals as well. Inthese instances, some component carriers may be overutilized and othercomponent carriers may be underutilized. To alleviate this problem,different anchor carriers can be selected for different user equipmentsto distribute the load. Also, the anchor carrier set for the differentuser equipments may be changed dynamically.

When the anchor carrier selection process completes, the number ofanchor carriers for the user equipment will typically change, preferablyto a lower number than there was before the change.

In another way, a control signaling hopping pattern, i.e. an anchorcarrier hopping pattern, can be provided to the user equipment. Theanchor carrier hopping pattern defines a sequence over time of anchorcarrier or carriers selected for the user equipment. The sequence can beat regular intervals such as at every subframe (1 ms), at every superframe (10 ms), and so on. By introducing hopping robustness to frequencyand time selective fading is introduced and the reselection signalingoverhead is reduced.

FIG. 2 illustrates an embodiment of a wireless network 200, whichincludes a base station 210 wirelessly communicating with userequipments 220-1, 220-2, and 220-3. The base station 210 is alsosometimes referred to as a Node B or eNB and examples of user equipments220 include a cellular phone, portable digital assistants (PDA) andmobile terminals.

The bidirectional zigzag arrowed lines from the base station 210 to theuser equipments 220 each represent a component carrier of an aggregatedwide bandwidth spectrum (see FIG. 1) used as anchor carriers. In FIG. 2,a single anchor carrier is in the anchor carrier set for the userequipment 220-1, two anchor carriers are included in the anchor carrierset for the user equipment 220-2, and three anchor carriers are includedin the anchor carrier set for the user equipment 220-3.

Note that the user equipments 220 can share a common component carrieras the anchor carrier. For example, one of the anchor carriers for theuser equipment 220-2 may be the same component carrier used as theanchor carrier for the user equipment 220-1.

In FIG. 2, it is assumed that the base station 210 is capable oftransmitting and the user equipments 220 are capable of receiving aplurality of component carriers where each component carrier isassociated with a bandwidth. That is, the wireless network 200 can be amulti carrier system such as a multi carrier LTE or GSM, WCDMA, and soon. The plurality of carriers can be such that there is at least one gapin the aggregated frequency spectrum represented by the plurality ofcarriers as illustrated in FIG. 1.

FIG. 3 illustrates an example method M300 to select one or more anchorcarriers for the user equipment 220 from the perspective of the userequipment 220. In the method, the user equipment 220 receivesinformation on the component carriers from the base station 210 that canpotentially be selected as the anchor carriers. For example, when theuser equipment 220 first connects to the base station 210, the basestation 210 may broadcast the information. At this point, it can beassumed that at least one component carrier is used as the anchorcarrier for the user equipment 220. In one example, a default carriermay be assigned as the anchor carrier for the user equipment 220 uponinitial connection with the base station 210.

Then in A320, the user equipment 220 monitors the signals transmittedover one or more of the plurality of component carriers from the basestation 210. It is preferred that the monitoring of the carriers beperformed periodically, such as every 50-100 ms. In this manner, powerconsumption is minimized.

In A330, the user equipment 220 makes a determination as to whether theanchor carrier set should be changed. An anchor carrier set is definedas a set of carriers that includes one or more anchor carriers used bythe user equipment 220 to receive control signals transmitted from thebase station 210. The user equipment 220 makes the determination basedon the monitoring performed in A320, i.e., it is determined whether thetriggering event has occurred.

In one embodiment, the user equipment 220 determines that the anchorcarrier set should be changed when a reliability of a non-anchorcomponent carrier (a carrier currently not in the anchor carrier set) isgreater than a reliability of an anchor carrier (a carrier currently inthe anchor carrier set). Note that the reliability comparison is madefrom the perspective of the user equipment 220.

Reliability may be determined based on signal-to-interference ratio(SIR), reference signal received power (RSRP), a data transmission rate,an error rate, a repeat request rate, etc. of each carrier. That is,between a first carrier currently not in the anchor carrier set and asecond carrier current in the anchor carrier set, the first carrier canbe determined to be more reliable than the second carrier when the SIRof the first carrier is higher than the second carrier, the RSRP of thefirst carrier is higher than the second carrier, the data transmissionrate of the first carrier is greater than the second carrier, and theerror rate of the first carrier is lower than that of the secondcarrier. Also, the repeat request rate of the first carrier could belower than that of the second carrier, for example, the HARQ (hybridautomatic repeat request) rate of the first carrier can be lower thanthat of the second carrier. In general, QoS (quality of service)parameters can be used for the reliability measurement.

If the user equipment 220 determines that the anchor carrier set shouldbe changed in A330, then the user equipment 220 can make a request tothe base station 210 to change the anchor carrier set in A340.Otherwise, the user equipment 220 can go back to monitor the carriers inA320.

FIG. 4 illustrates an example method to perform A340 of FIG. 3. In FIG.4, the user equipment 220 determines whether the first carrier, i.e.,the current non-anchor carrier, meets a predetermined minimumreliability threshold in A410. That is, the user equipment 220determines whether the first carrier is sufficient on its own to serveas the sole anchor carrier. If the first carrier meets the predeterminedminimum reliability threshold, then in A420, the user equipment 220makes a request to the base station 210 to include only the firstcarrier in the anchor carrier set. This allows the receivers of the userequipment 220 configured to listen on other component carriers to be putinto a power conservation mode. Examples of power conservation modesinclude turning off the receiver, turning on a DRX (discontinuousreception) mode for the receiver, narrowing the frequency of thereceiver (in case of adaptable bandwidth receiver), and so on.

On the other hand, if the first carrier does not meet the predeterminedminimum reliability threshold in A410, then the user equipment 220 makesa request to the base station 210 to include multiple carriers into theanchor carrier set in A430 which can include the first carrier. Here,the multiple carriers can be chosen from the plurality of carriers towhich the user equipment 220 is capable of listening so as to minimizethe number of anchor carriers in the anchor carrier set necessary tomeet the predetermined minimum reliability threshold. The predeterminedreliability threshold may be based on the reliability parameters such asthe parameters discussed above.

In FIG. 2, the user equipment 220 receives control signals from a singlebase station 210. That is, the anchor carriers are all from the samebase station 210. However, it is possible to include multiple basestations. In an embodiment illustrated in FIG. 5, the anchor carrier setfor the user equipment 520 can include component carriers from differentbase stations 510-1 and 510-2. In this instance, the user equipment 520can monitor the signals carried on component carriers used by both basestations 510. In FIG. 5, one of the base stations 510, such as the basestation 510-1, is assumed to be the serving base station 510 for theuser equipment 520.

FIG. 6 illustrates an example method M600 to select anchor carriers forthe user equipment when there are multiple base stations. In the method,the user equipment 520 can receive information of component carriersthat can be used as anchor carriers in A610. In this situation, the userequipment 520 receives information on component carriers of multiplebase stations 510.

In A620, the user equipment 520 monitors the component carriers of therespective base stations 510. Based on the monitoring, the userequipment 520 makes a determination on whether the anchor carrier setshould be changed in A630, i.e., determines whether the triggering eventhas occurred. If the user equipment 520 makes such determination, thenthe user equipment 520 makes a request to switch the anchor carrier setin A640. Otherwise, the user equipment 520 goes back to monitoring thecarriers in A620. Note that A610, A620, and A630 in FIG. 6 are similarto A310, A320 and A330 in FIG. 3, respectively. The difference is thatcomponent carriers of multiple base stations 510 are considered in FIG.6.

FIG. 7 illustrates an example method to perform A640 of FIG. 6. In FIG.7, the user equipment 520 determines whether the first carrier meets thepredetermined minimum reliability threshold in A710. If so, then theuser equipment 520 makes a request to include only the first carrier inthe anchor carrier set in A720. Otherwise, in A730, the user equipment520 makes a request to include multiple carriers in the anchor carrierset. Again, the multiple carriers are chosen to minimize the number ofcarriers to meet the predetermined minimum reliability threshold. Notethat the multiple carriers need not be all from a single base station.Carriers from multiple base stations 510 can be selected to meet thepredetermined minimum reliability threshold while minimizing the numberof carriers selected.

FIG. 8 illustrates a method to perform A720 of FIG. 7 in the multiplebase station environment. Here, the user equipment 520 has determinedthat the first carrier is sufficient on its own. Thus, if the firstcarrier is not from the current serving base station 510-1, then ahandoff is required.

In A810, the user equipment 520 determines whether a handoff isnecessary. That is, it is determined whether the first carrier is from abase station that is not the current serving base station. If suchdetermination is made, then in A820, the user equipment 520 makes arequest to the current serving base station 510-1 to be handed off tothe new serving base station 510-2. Once the handoff is completed, thenin A830, the user equipment 520 makes a request to the new serving basestation 510-2 to include only the first carrier in the anchor carrierset. If the handoff is not required, then in A840, the user equipment520 makes a request to include only first carrier to be in the anchorcarrier set to the current serving base station 510-1.

As noted previously, one advantage of minimizing the number of anchorcarriers is that power of the user equipment may be conserved. Forexample, the user equipment may include a plurality of fixed narrowbandwidth receivers each configured to receive signals on particularcomponent carriers. By minimizing the number of anchor carriers, thereceivers that do not correspond to the anchor carriers can be put inpower conservation mode. The power conservation mode can include any oneor more of turning off the receiver, putting the receiver in a periodicmonitoring mode, enabling a DRX (discontinuous reception) mode, and soon.

In another example, the user equipment may include one or more adaptablebandwidth receivers where the frequency range of each receiver can bedynamically adapted. Here, a receiving frequency range of the receiverscan be narrowed to exclude non-anchor carriers for power conservation.Of course, the user equipment can include both fixed and adaptablebandwidth receivers.

The embodiments illustrated in FIGS. 1-8 can work very well for a userequipment that is either stationary or slow moving. In the slow movingsituation, the quality/reliability of the component carriers areunlikely to change from the perspective of the user equipment. However,for a fast moving user equipment, the situation can be very different,as illustrated in FIG. 9. As illustrated, the user equipment 920 is atsignificantly different positions at time t1 and at time t2. The anchorcarrier set that was sufficient at time t1 may not be sufficient at timet2, and the anchor carrier set would need to be changed for the userequipment 920 at time t2. If the user equipment 920 is very fast moving,the anchor carrier set would be changed frequently.

Even under the fast moving user equipment scenario, the methods outlinedin FIGS. 2-8 can be used with good results. However, it may be moreresource efficient to anticipate the need for frequent anchor carrierset changes and to provide the information to the user equipment 920 inadvance. In one embodiment, an anchor hopping pattern provided to theuser equipment 920. The anchor hopping pattern specifies a sequence overtime of one or more anchor carriers to be used by the user equipment 920to receive the control signals transmitted by the base station 910.

The hopping pattern can be user equipment specific and be based on theidentification of the user equipment 920. The hopping pattern can alsobe cell specific based on some cell specific hopping pattern. Thehopping pattern could be such that the user equipment listens on acontrol channel on a particular component carrier for a superframe (10ms long in LTE) and then jump to another component carrier or carriers.Then the user equipment 920 can receive the message and detect thecontrol signals on the component carrier(s) according to the hoppingpattern. An advantage of applying the anchor carrier hopping pattern isthat it introduces robustness to the frequency and/or time selectivefading, and at the same time, reduces the anchor carrier reselectionsignaling overhead associated with the methods illustrated in FIGS. 2-8.

FIG. 10 illustrates an example method M1000 to implement the carrierhopping process described above. In A1010, the user equipment 920receives information regarding the component carriers from the basestation 910.

The hopping pattern may be provided because the base station 910determines that there is a need for the hopping pattern. For example,the base station 910 can determine that the hopping pattern is needed inA1020 because the user equipment 920 is moving at a speed greater than apredetermined minimum rate. In one embodiment, a strength of the uplinktransmission from the user equipment 920 can be measured by the basestation 910 over time to determine the speed of movement of the userequipment 920.

The hopping pattern may also be provided because the user equipment 920determines the need. In A1030, the user equipment 920 itself candetermine that it is moving at a rate greater than the predeterminedminimum rate, and thus, makes a request for the hopping pattern. Forexample, the user equipment 920 may include a location detection unitsuch a GPS unit.

When the need for the hopping pattern is determined in A1020 or therequest for hopping pattern is made by the user equipment in A1030, thenthe base station 920 provides the hopping pattern to the user equipment910 in A1040. Then in A1050, the user equipment 920 adapts the receiversto receive the control signals transmitted from the base station 910 bysequencing through the anchor carriers according to the anchor carrierhopping pattern.

In the example methods and embodiments discussed above, the selection ofthe anchor carriers in the anchor carrier set is based on considerationsregarding the user equipment. However, the composition of the anchorcarrier set for a user equipment may also be based on the considerationof the network as a whole. For example, there may be a capacity issue inthe network. Over time, some component carriers may be overutilized andother component carriers may be underutilized. The overutilization canstem from not only transmitting control signals to the user equipments,but also from using the carrier to carry data between the base stationsand the user equipments.

FIG. 11 illustrates a method to redistribute anchor carriers, i.e.,update anchor carrier sets, for load management. In FIG. 11, the basestation monitors, in A1110, the load on each of the plurality ofcomponent carriers it uses for communication with the user equipments.Based on the monitoring, the base station determines whether anchorcarrier sets should be updated to the user equipments in A1120. If suchdetermination is made, then in A1130, the base station notifies one ormore user equipments to switch anchor carriers, i.e., to update theanchor carrier set. That is, the base station informs the userequipments on which component carrier or carriers the control signalsfor that particular user equipment will be transmitted on. Afterwards,the base station transmits the control signals accordingly.

There can be a host of reasons to initiate updates of the anchor carriersets. For example, the SIR of an anchor carrier used by one of the userequipments may fall below the predetermined minimum SIR threshold. Otherreasons include: an error rate of data carried over an anchor carrierpasses over a predetermined error rate threshold; a repeat request rateof data transmitted over an anchor carrier falls below a predeterminedrepeat request rate threshold; a number of user equipments being servedby the base station over one carrier is greater than a number of userequipments being served by the base station over another carrier by atleast a predetermined number; an amount of data transmitted over onecarrier is greater than an amount of data transmitted over anothercarrier by at least a predetermined amount; and so on.

FIG. 12 illustrates an embodiment of the user equipment 220, 520 and920, which includes a processing unit 1210, a monitoring unit 1220, acommunication unit 1230 and a location detection unit 1240. Themonitoring unit 1220 can, e.g., monitor the quality of the signals oncarriers transmitted by the base stations 210, 510, 910 and the locationunit 1240, such as the GPS unit, can determine the present location ofthe user equipment 220, 520, 920 as well as determining the rate ofmovement.

The communication unit 1230 is arranged to communicate with the basestations 210, 510, 910 and can include any combination of fixedbandwidth receivers and adaptable bandwidth receivers. If only fixedbandwidth receivers are considered, then the communications unit 1230 ispreferred to include a plurality of receivers, where each receiver isconfigured to listen on one of the plurality of component carriers. Ifonly adaptable bandwidth receivers are considered, then there can be oneor more of these receivers. If a combination is considered, then therecan be one or more fixed bandwidth receivers and one or more adaptablebandwidth receivers.

The processing unit 1210 is arranged to control the operations of thecomponents of the user equipment 220, 520, 920 including the monitoringunit 1220, the communication unit 1230 and the location unit 1240 toperform the methods described above.

FIG. 13 illustrates an embodiment of a base station 210, 510, 910 asillustrated in FIGS. 2, 5 and 9. The base station 210, 510, 910 includesa processing unit 1310, a monitoring unit 1320 and a communication unit1330. The monitoring unit 1320 is arranged to monitor, e.g., the load onthe component carriers used by the base station 210, 510, 910. Thecommunication unit 1330 is arranged to communicate with the userequipments 220, 520, 920 in the network. The processing unit 1310 isarranged to control the operations of the components of the base station210, 510, 910 including the monitoring unit 1320 and the communicationunit 1330 to perform the methods as described above.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the invention but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. Therefore, it will be appreciated that the scope ofthe present invention fully encompasses other embodiments which maybecome obvious to those skilled in the art, and that the scope of thepresent invention is accordingly not to be limited. All structural, andfunctional equivalents to the elements of the above-described preferredembodiment that are known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed hereby. Moreover, it is not necessary for a device or methodto address each and every problem described herein or sought to besolved by the present technology, for it to be encompassed hereby.Furthermore, no element, component, or method act in the presentdisclosure is intended to be dedicated to the public.

What is claimed is:
 1. A method for operating a user equipment of awireless network, comprising: making a determination as to whether ananchor carrier set should be changed, wherein the anchor carrier setincludes one or more anchor carriers used by the user equipment toreceive control signals transmitted from a base station; and making arequest to the base station to change the anchor carrier set when it isdetermined that the anchor carrier set should be changed, wherein it isdetermined that the anchor carrier set should be changed when areliability of a first carrier is greater than a reliability of a secondcarrier from a perspective of the user equipment, wherein the firstcarrier is currently not in the anchor carrier set and the secondcarrier is currently in the anchor carrier set, and wherein the act ofmaking the request to the base station to change the anchor carrier setcomprises: making a determination as to whether the first carrier meetsa predetermined minimum reliability threshold when it is determined thatthe anchor carrier set should be changed; and making a request to thebase station to include multiple carriers into the anchor carrier setwhen it is determined that the first carrier does not meet thepredetermined minimum reliability threshold, wherein the first carrieris included in the anchor carrier set after the change.
 2. The method ofclaim 1, wherein the user equipment is configured to communicate withthe base station over a plurality of carriers with each carrier beingassociated with a bandwidth, and wherein there is at least one gap in afrequency spectrum represented by the plurality of carriers.
 3. Themethod of claim 1, wherein the first carrier is determined to be morereliable than the second carrier when any one or more of the followingis true: a signal-to-interference ratio (SIR) of the first carrier ishigher than a SIR of the second carrier, a reference signal receivedpower (RSRP) of the first carrier is higher than a RSRP of the secondcarrier, a data transmission rate of the first carrier is greater than adata transmission rate of the second carrier, an error rate of the firstcarrier is lower than an error rate of the second carrier, and a repeatrequest rate of the first carrier is lower than a repeat request rate ofthe second carrier.
 4. The method of claim 1, wherein the act of makingthe request to the base station to change the anchor carrier set furthercomprises making a request to the base station to include only the firstcarrier in the anchor carrier set when it is determined that the firstcarrier meets the predetermined minimum reliability threshold.
 5. Themethod of claim 1, wherein the multiple carriers are chosen from theplurality of carriers that the user equipment is configured to listen toso as to minimize a number of anchor carriers necessary to meet thepredetermined minimum reliability threshold.
 6. The method of claim 4,wherein the base station is a current serving base station, and whereinthe act of making the request to the base station to include only thefirst carrier in the anchor carrier set comprises: making adetermination whether a handoff to a new serving base station isrequired when it is determined that the first carrier meets thepredetermined minimum reliability threshold; making a request to thecurrent serving base station for the handoff when it is determined thatthe handoff is required; and making a request to the new serving basestation to include only the first carrier in the anchor carrier setafter the handoff is requested.
 7. The method of claim 1, furthercomprising putting receivers of the user equipment configured to receivesignals on carriers not in the anchor carrier set into a powerconservation mode.
 8. The method of claim 7, wherein putting each of thereceivers in the conservation mode includes any one or more of turningoff the receiver, enabling a DRX mode for the receiver, and narrowing areceiving frequency range of the receiver to exclude the non-anchorcarriers.
 9. The method of claim 1, further comprising: receiving ananchor hopping pattern from the base station; and adapting one or morereceivers of the user equipment to receive control signals transmittedfrom the base station according to the anchor hopping pattern, whereinthe anchor hopping pattern specifies a sequence over time of one or moreanchor carriers used by the user equipment to receive the controlsignals transmitted by the base station.
 10. The method of claim 9,further comprising: making a request to the base station for the anchorhopping pattern when it is determined that the user equipment is movingat a rate that is at or greater than a predetermined minimum speedthreshold.
 11. The method of claim 1, wherein a number of anchorcarriers in the anchor carrier set is changed after making the request.12. A user equipment of a wireless network comprising: a communicationsunit configured to communicate with a base station; and a processingunit configured to: make a determination as to whether an anchor carrierset should be changed, wherein the anchor carrier set includes one ormore anchor carriers used by the user equipment to receive controlsignals transmitted from a base station; and make a request to the basestation, via the communications unit, to change the anchor carrier setwhen it determines that the anchor carrier set should be changed,determine that the anchor carrier set should be changed when areliability of a first carrier is greater than a reliability of a secondcarrier, wherein the first carrier is currently not in the anchorcarrier set and the second carrier is currently in the anchor carrierset, wherein the processing unit is configured to request the change tothe anchor carrier set by: making a determination as to whether thefirst carrier meets a predetermined minimum reliability threshold whenit determines that the anchor carrier set should be changed; and makinga request to the base station to include multiple carriers into theanchor carrier set when it determines that the first carrier does notmeet the predetermined minimum reliability threshold, and wherein thefirst carrier is included in the anchor carrier set after the change.13. The user equipment of claim 12, wherein the communications unit isconfigured to communicate with the base station over a plurality ofcarriers with each carrier being associated with a bandwidth, andwherein there is at least one gap in a frequency spectrum represented bythe plurality of carriers.
 14. The user equipment of claim 12, whereinthe processing unit is configured to determine that the first carrier ismore reliable than the second carrier when any one or more of thefollowing is true: a signal-to-interference ratio (SIR) of the firstcarrier is higher than a SIR of the second carrier, a reference signalreceived power (RSRP) of the first carrier is higher than a RSRP of thesecond carrier, a data transmission rate of the first carrier is greaterthan a data transmission rate of the second carrier, an error rate ofthe first carrier is lower than an error rate of the second carrier, anda repeat request rate of the first carrier is lower than a repeatrequest rate of the second carrier.
 15. The user equipment of claim 12,wherein the processing unit is further configured to request the changeto the anchor carrier set by making a request to the base station toinclude only the first carrier in the anchor carrier set when it makesthe determination that the first carrier meets the predetermined minimumreliability threshold.
 16. The user equipment of claim 12, wherein themultiple carriers are chosen from the plurality of carriers thecommunications unit is configured to listen to so as to minimize anumber of anchor carriers necessary to meet the predetermined minimumreliability threshold.
 17. The user equipment of claim 15, wherein thebase station is a current serving base station, and wherein theprocessing unit is configured to: make a determination whether a handoffto a new serving base station is required when it determines that thefirst carrier meets the predetermined minimum reliability threshold;make a request to the current serving base station for the handoff whenit determines that the handoff is required; and make a request to thenew serving base station to include only the first carrier in the anchorcarrier set after the handoff is requested.
 18. The user equipment ofclaim 12, wherein the processing unit is configured to put receivers ofthe communications unit configured to receive signals on carriers not inthe anchor carrier set into a power conservation mode.
 19. The userequipment of claim 18, wherein putting each of the receivers in theconservation mode includes any one or more of turning off the receiver,enabling a DRX mode for the receiver, and narrowing a receivingfrequency range of the receiver to exclude the non-anchor carriers. 20.The user equipment of claim 12, wherein the communication unit includes:two or more fixed bandwidth receivers with each receiver configured toreceive signals on corresponding carriers transmitted by the basestation, one or more adaptive bandwidth receivers with each receiverconfigured to be dynamically adaptable to receive signals on one or morecarriers transmitted by the base station, or one or more fixed bandwidthreceivers and one or more adaptive bandwidth receivers.
 21. The userequipment of claim 12, wherein the processing unit is configured to:receive, via the communications unit, an anchor hopping pattern from thebase station, and adapt one or more receivers of the communications unitto receive the control signals transmitted from the base stationaccording to the anchor hopping pattern, wherein the anchor hoppingpattern specifies a sequence over time of one or more anchor carriersused by the user equipment to receive the control signals transmitted bythe base station.
 22. The user equipment of claim 21, furthercomprising: a location detection unit configured to determine a locationof the user equipment, wherein the processing unit is configured to:make a determination, via the location detection unit, that the userequipment is moving at a predetermined minimum speed threshold orgreater; and make a request to the base station, via the communicationsunit, for the anchor hopping pattern when it determines that the userequipment is moving at the predetermined minimum speed threshold orgreater.
 23. A method for operating a user equipment of a wirelessnetwork, comprising: making a determination as to whether an anchorcarrier set should be changed, wherein the anchor carrier set includesone or more anchor carriers used by the user equipment to receivecontrol signals transmitted from a base station; making a request to thebase station to change the anchor carrier set when it is determined thatthe anchor carrier set should be changed; receiving an anchor hoppingpattern from the base station; adapting one or more receivers of theuser equipment to receive control signals transmitted from the basestation according to the anchor hopping pattern, wherein the anchorhopping pattern specifies a sequence over time of one or more anchorcarriers used by the user equipment to receive the control signalstransmitted by the base station; and making a request to the basestation for the anchor hopping pattern when it is determined that theuser equipment is moving at a rate that is at or greater than apredetermined minimum speed threshold.
 24. A user equipment of awireless network comprising: a communications unit configured tocommunicate with a base station; and a processing unit configured to:make a determination as to whether an anchor carrier set should bechanged, wherein the anchor carrier set includes one or more anchorcarriers used by the user equipment to receive control signalstransmitted from a base station; and make a request to the base station,via the communications unit, to change the anchor carrier set when itdetermines that the anchor carrier set should be changed, receive, viathe communications unit, an anchor hopping pattern from the basestation, adapt one or more receivers of the communications unit toreceive the control signals transmitted from the base station accordingto the anchor hopping pattern, wherein the anchor hopping patternspecifies a sequence over time of one or more anchor carriers used bythe user equipment to receive the control signals transmitted by thebase station, a location detection unit configured to determine alocation of the user equipment, wherein the processing unit isconfigured to: make a determination, via the location detection unit,that the user equipment is moving at a predetermined minimum speedthreshold or greater; and make a request to the base station, via thecommunications unit, for the anchor hopping pattern when it determinesthat the user equipment is moving at the predetermined minimum speedthreshold or greater.
 25. A method for operating a base station of awireless network, comprising: making a determination as to whetheranchor carrier sets should be updated for one or more user equipments,wherein each anchor carrier set includes one or more anchor carriersused by the base station to transmit control signals to the one or moreuser equipments; transmitting to the one or more user equipments anotification of the anchor carrier set update when it is determined thatthe anchor carrier sets should be updated; making a determination as towhether an anchor hopping pattern is needed for a user equipment;providing the anchor hopping pattern to the user equipment when it isdetermined that the anchor hopping pattern is needed; and transmittingcontrol signals to the user equipment according to the anchor hoppingpattern, wherein the anchor hopping pattern specifies a sequence overtime of one or more anchor carriers used by the base station to transmitthe control signals to the user equipment, and wherein it is determinedthat the anchor hopping pattern is needed when: it is determined that auser equipment is moving at a rate that is at or greater than apredetermined minimum speed threshold, or a request for the anchorhopping pattern is received from the user equipment.
 26. A base stationof a wireless network, comprising: a communications unit configured tocommunicate with the user equipment; and a processing unit configuredto: make a determination as to whether anchor carrier sets should beupdated for one or more user equipments, wherein each anchor carrier setincludes one or more anchor carriers used by the base station totransmit control signals to the one or more user equipments; transmit tothe one or more user equipments, via the communications unit, anotification of the anchor carrier set update when it determines thatthe anchor carrier sets should be updated; make a determination as towhether an anchor hopping pattern is needed for a user equipment;provide the anchor hopping pattern to the user equipment, via thecommunications unit, when it is determined that the anchor hoppingpattern is needed; and transmit control signals to the user equipment,via the communications unit, according to the anchor hopping pattern,wherein the anchor hopping pattern specifies a sequence over time of oneor more anchor carriers used by the base station to transmit the controlsignals to the user equipment, wherein the processing unit is configuredto determine that the anchor hopping pattern is needed when: theprocessing unit determines that a user equipment is moving at a ratethat is at or greater than a predetermined minimum speed threshold, or arequest for the anchor hopping pattern is received from the userequipment.